This invention relates to a printing roller, and more particularly to the type of roller which comprises a mandrel fitted with a removable cylinder.
In certain types of printing, a printing cylinder is employed, the purpose of which is to carry ink for printing operations. The ink is transferred from a cylindrical surface to the surface of the paper which runs between an impression roller and the printing cylinder. Printing rollers are used to support flexible printing plates, and the roller mandrels are designed to be rotatably mounted in a printing machine. The cylinder is normally removable from the mandrel to allow the printing plate to be changed without changing the entire roller.
One common method for changing such printing cylinders is utilized where the cylinders are attached to outer journals. In particular, the cylinder is slid over the journals, and through heat treatment processes, the cylinders are shrunk onto the journals at their ends, thereby forming a frictional fit between the rotating journals and printing cylinder carried thereon. In order to remove the cylinder, heat is applied to the journal-cylinder interface allowing expansion of the cylinder to permit the cylinder to be removed from the journal.
Various systems have been proposed to eliminate the heat treatment process for removing printing rollers from the journal or mandrel assembly. Hydraulic systems have been suggested, and one such system is identified in U.S. Pat. No. 3,378,902 issued Apr. 23, 1978 to Rolf Hoexter. A relatively complex and difficult system is set forth in which precise drilling is suggested for forming thin-walled pressure sections to carry a radial pressure outwardly attempting to fix the printing cylinder to the hub section mounted between two outer collets.
In another system, as set forth in U.S. Pat. No. 4,150,622 entitled Printing Roller issued on Apr. 24, 1979 to Joseph A. Stollenwerk, a hydraulic system employing air pressure is employed in which compressible rings are adapted to be forced outwardly to hold the outer printing cylinder.
An object of this invention is to provide an improved printing roller of the type in which the printing cylinder is removed from the mandrel assembly.
Another object of this invention is to provide such a removable cylinder construction, which is easy to utilize, susceptible of widescale use, and reliable in operation.
Yet another object of this invention is to provide such a printing roller construction in which the cylinder is securely maintained in position, with respect to the mandrel.
Yet another object of this invention is to provide such a printing cylinder construction which may be easy to fabricate, minimize precise drilling requirements, and be effective in operation.
Another object of this invention is to provide such a printing roller in which the cylinder is attached to the mandrel at the outer sections with a long central thin tubular section being provided as part of a three piece mandrel assembly.
Yet another object of this invention is to provide such a printing roller assembly in which the hydraulic system employed is a fluid hydraulic system, and further in which the hydraulic actuating piston assembly is integrally formed in the mandrel assembly.
Other objects, advantages and features of this invention will become more apparent from the following description.